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I would like to know how to force a Mac to recheck the USB connections without needing to physically unplug and plug them again. Is there a Terminal command for this?

Context: I have a USB audio connection (an amplifier with a DAC) directly connected to my Mac (description below). With everything on, once I plug the USB to the Mac the audio output is correctly detected and it appears in the menu bar under the sound icon. Also, as expected, when I power off the amplifier the USB audio output is no longer available (it disappears from the sound menu).

The problem appears when I power on the amplifier again, since my Mac does not recognize the USB sound output. To make it work, I need to physically unplug and plug again the USB with the amplifier turned on.

Thus, if there was some system command (either through Terminal or by other means) to force the Mac to recheck the USB connections that would be time saving for me.

Configuration: The issue occurs on two Macs, both of them with Big Sur 11.4. One is a Mac Pro 2013 and the other a Macbook Pro 2018 13". I also had the same problem with Catalina. The DAC/Amplifier is an Emotiva TA 100. For either mac, I use a single cable directly connected between the computer and the amplifier.

Update (16/October/2021): I "solved" my problem by buying another DAC. I understand that my previous one had some problem, but it would be nice to have a software way to circumvent the issue.

Davi
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  • Is the DAC connected directly to a USB port on both Macs, or through a hub of some sort? – IconDaemon Jul 05 '21 at 00:31
  • @IconDaemon, it is connected directly to the mac, no hub or other connections. – Davi Jul 05 '21 at 01:52
  • I just found this similar question https://apple.stackexchange.com/questions/271252/disconnect-connect-usb-device-from-command-line . However, the provided answer is not a valid one, since it only applies to smart USB hubs; which is not my case. – Davi Jul 10 '21 at 22:06
  • Can you see the device in the app Audio MIDI Setup? It's in /Applications/Utilities. – IconDaemon Jul 10 '21 at 22:38
  • Yes, when the dac is recognized, I can see it in Audio MIDI setup. – Davi Jul 11 '21 at 17:07
  • Additional piece of information: after the DAC is recognized, if I turn it off only for a brief period of time (some minutes), then after turning it on it is properly recognized. This is puzzling to myself, but it may be relevant to understand what is happening. – Davi Jul 11 '21 at 17:11
  • Next time it disappears, see if running Audio MIDI Setup 'recognizes' the dac, and makes it visible again. – IconDaemon Jul 11 '21 at 19:33
  • @IconDaemon, I tried several times, but the Audio MIDI Setup seems to make no difference. If the dac is recognized, the app works normally. If the dac is not recognized, launching the app makes no difference: it continues to be unrecognized. – Davi Jul 16 '21 at 04:04

1 Answers1

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You could try launching System Information and looking at the USB section. Connected devices show up there and CMD-R refreshes the information. That might cause the Mac to again recognize the amplifier.

apta
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  • I tried now, but it didn't helped. The DAC/Amplifier (Emotiva TA 100) didn't show up when I entered the system information. After unplugging and plugging it again, it was recognized in the Sound menu bar icon. And after leaving and returning to system information, it appeared in the system information. – Davi Jul 05 '21 at 15:04
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    This answer won't work. Cmd-R only refreshes the display - it doesn't in any way cause the Mac to actually do something with the USB ports, such as "recognizing" or "go looking for" new devices or anything like that. – jksoegaard Jul 05 '21 at 18:04